Process for treatment of oil-containing seeds

ABSTRACT

OILSEED MATERIAL SUCH AS OILSEEDS OR OIL-CONTAINING BRAN CONTAINING A SUBSTANTIAL AMOUNT OF UNDENATURED PROTEIN AND IN EXCESS OF 6% BY WEIGHT OF WATER IS SUBJECTED TO GRINDING UNDER WET MILLING CONDITIONS IN THE PRESENCE OF FROM ABOUT 1.5 TO 4, PREFERABLY ABOUT 2 TO ABOUT 3, TIMES ITS WEIGHT OF MENTHANOL, ETHANOL, ACETONE OR MIXTURES THEREOF, CONTAINING NO MORE THAN 2% BY WEIGHT OF WATER, TO REMOVE FROM THE MATERIAL WATER, CARBOHYDRATES, PIGMENT MATERIAL, WAX MATERIAL, ODOR AND TASTE PRINCIPLES, AND FREE FATTY ACIDS, AND TO PRECONDITION THE MATERIAL BY OPENING THE CELL STRUCTURE; SEPARATING THE SOLID MATERIAL FROM THIS FIRST LIQUID EXTRACT AND FURTHER EXTRACTING THE SOLID MATERIAL WITH A FAT SOLVENT, SEPARATING THE OIL-BEARING EXTRACT AND FURTHER SEAPRATING THE TWICE EXTRACTED SOLID MATERIAL INTO A FINE PARTICLE FRACTION HIGH IN UNDENATURED PROTEIN AND A COARSE PARTICLE FRACTION HIGH IN FIBER.

United States Patent O /5 Int. Cl. A233 1/12, 1/14;C11b 1/10 US. Cl.260-4235 larms ABSTRACT OF THE DISCLOSURE Oilseed material such asoilseeds or oil-containing bran containing a substantial amount ofundenatured protein and in excess of 6% by weight of water is subjectedto grinding under wet milling conditions in the presence of from about1.5 to 4, preferably about 2 to about 3, times its weight of methanol,ethanol, acetone or mixtures thereof, containing no more than 2% byweight of water, to remove from the material water, carbohydrates,pigment material, wax material, odor and taste principles, and freefatty acids, and to precondition the material by opening the cellstructure; separating the solid material from this first liquid extractand further extracting the solid material with a fat solvent, separatingthe oil-bearing extract and further separating the twice extracted solidmaterial into a fine particle fraction high in undenatured protein and acoarse particle fraction high in fiber.

CROSS REFERENCE TO RELATED CASE This is a continuation-in-part of ourcopending application Ser. No. 888,856, filed Dec. 29, 1969, nowabandoned.

BACKGROUND OF THE INVENTION This invention relates to an improvedprocess for separately recovering oil and a protein-rich powder fromseeds or brans.

DESCRIPTION OF THE PRIOR ART In the conventional treatment ofoil-bearing seeds, the seeds are hulled, crushed, rolled, and flakedunder high pressure and are subjected to other treatments prior toextracting the oils with fat solvents. The treatments conventionallyinclude a drying step to reduce the moisture content to approximately 5%by weight. Examples of such seeds and seed materials are perillaocimoides, flax, hemp, paulownia, sunflower, soybeans, cotton, sesame,rape, castor, kapok, olive, camellia, peanut, the embryo bud of Indiancom (com germ) and rice bran.

The oil produced from these prior conventional methods requiressubsequent refining steps to remove carbohydrates, color material,waxes, free fatty acids and various odor and taste principles; and thesteps of refining are technologically complex and the processesinevitably result in loss of valuable oil. In addition, the non-oilresidue of the oil seed material, though containing substantial amountsof protein, is difficult to process so as to recover good qualityundenatured protein. Often- "ice times the pretreatrnents prior to oilextraction have involved heating steps that, in themselves, causedenaturing of the protein.

The water that exists in seasoned stabilized oil seeds is found to alarge extent within the cell and the amount does not vary substantiallyunder ordinary methods of storage, transpartation or preservation. It isgenerally accepted that etfective oil extraction from such seeds withthe conventionally used fat solvents requires that the seeds have atotal water content of 5% by weight, or less. Owing to the fact thatthis moisture is distributed within the refractory cell structure,conventional drying, as by ovens or grain driers, subjects the oilseedmaterial to excessive temperatures detrimental to the quality of boththe oil and the protein.

In some pretreatments of such oil-bearing materials prior to solventextraction, the comminuting eifect of the mechanical grinding is said tobe intensified by adding water and organic solvent to a wet grindingstep or by immersing the seed material in water prior to wet grinding.Water, used in this way, increases the viscosity of the ground material,and it is not effectively oil extractable unless large excesses of fatsolvents are used, up to several times the quantity used, say in thepractice of this invention. This use of water also has the disadvantageof causing expansion or swelling of the fiber, carbohydrate and proteinconstituents of the seed material, and partial dissolving of thecarbohydrate. This not only increases the viscosity of the mixture butalso renders diflicult the separation of the solids from the extract,and tends to cause colloidal suspension of oil and protein with theconsequential difliculties of separation and recovery.

The solids separated from these prior processes using water naturallycontain large proportions of water, and the conventional drying requiresprolonged times at high temperateures, which is detrimental to thequality of both the oil and the protein, constituents, and moreoverrenders decoloring and refining unduly complex.

It is known to subject such material as safllower seed material to a wetmilling step using an oil solvent to achieve difierential size reductionin the solvent of the kernel material containing high protein and thehull material containing high fiber content. See US. Pat. 3,542,559. Thesolvent bearing the extracted safliower oil is separated, and theresidue material can then be screened to separate it into a protein-richfine fraction and a high-fiber coarser fraction. This prior art process,however does not provide for removal or adjustment of water content, andthe residue after oil extraction contains all the oil-insolubleimpurities originally present in the raw material.

BRIEF DESCRIPTION OF THE INVENTION This invention relates to a processfor separately recovering oil and a protein-rich powder from oil bearingmaterial comprising mixing one part by weight of an oil bearing materialof the group consisting of oil seeds and oil-containing bran, said oilbearing material also containing a substantial amount of undenaturedprotein and in excess of 6% by weight of Water, with a first solventconsisting of about 1.5 to four parts by weight of a water-misciblesolvent selected from the group consisting of methanol, ethanol andacetone and mixtures thereof, said first solvent containing no more than2% by weight of water; grinding the mixture under wet millingconditions; separating the milled mixture into a first liquid phase anda first solid phase; mixing said first solid phase with anoil-extracting organic solvent until the oil in said first solid phasedissolves in said oil-extracting solvent to obtain a second liquid phaseenriched with oil and a second solid phase; separating the second liquidphase from the second solid phase and recovering oil from said secondliquid phase; drying the second solid phase to obtain a finely dividedpowder; and passing the powder through a sieve of a size in the range of60-100 mesh to separate the powder into a protein-rich fraction whichpasses through the sieve and a fraction of composed primarily ofindigestible substance which remains on the sieve.

The term grinding under wet milling conditions as used in thisspecification and claims refers to those milling processes as are usedconventionally in the wet milling of grain, using a dispersion mill, ahomogenizer or the like. It refers to the comminution or levigationaction simultaneously with emulsification or intimate mixing with theliquid substrate in which the comminution is being carried out, thatcharacterizes this kind of milling.

The object of the present process is to separate, in a short time, (1)oil of good quality, (2) nutritious components (vitamins, starch, etc.)containing protein of good quality and which have subjected to minimumdenaturing action, and (3) fibers, directly from seeds and the likecontaining fats and oils.

The present process is applied to the raw materials used for extractionof ordinary fats and oils, but particularly suitable to the oil bearingmaterials previously mentioned, i.e. seeds of perilla ocimoides, flax,hemp, paulownia, sunflower, soybean, cotton seed, sesame, rapeseed,castor-oil plant seed, kapok, olive, camellia seed, peanut, and theembryo bud of Indian corn (corn germ), and rice bran. These seeds aretreated in their raw, as harvested condition, that is, they have notbeen subjected to any hulling, water dipping, crushing or flaking,although they may have been subjected to surface cleaning and drying. Inthe case of corn germ and rice bran, they are treated as received fromthe corn germ or rice bran separating equipment. These seed contain 615%by weight of water (usually about The present process does not useexcessive temperatures and permits adjustment of the water content tothat which is most suitable for oil extraction.

In the present process, the raw material is first ground under wetmilling conditions in an organic solvent (methanol, ethanol, acetone, ormixtures thereof) containing no more than 2% water in which neutral oilis relatively insoluble, but which mixes freely with water. The quantityof solvent used in the first step is sufficient if it is 1.5 to 4,preferably about 2 to 3, times by weight the quantity of raw materialtreated. The affinity of these organic solvents for water is so greatthat they act on the water present in the cells of the raw materialthrough the cell-wall to eflect a kind of dehydration. The watercontained in the cell is extracted by this action through the cell-wall,so that the cell-wall itself is weakened and becomes relatively easilyruptured. At this time if the wet grinding operation is simultaneouslyapplied to the mixture, the substances of the mixture are readilyseparated into fibrous part, hull part, and ruptured cell-wall part, andthe water content can be adjusted to an optimum condition for subsequentremoval of fat.

The present process is based in part on this above discovery of theunexpectedly advantageous preconditioning result of this first stage oftreatment.

As organic solvents which can fully develop the advantages of thepresent process, methanol, ethanol, acetone and mixtures thereof areespecially suitable. The quantity of solvent is preferably 2 to 3 times(by weight) the quantity of raw material. This quantity is satisfactoryto fully realize the above advantages, to facilitate the reclamation ofthe solvent, t9 increa the gfinding efi'iciency, and to minimize theloss of neutral oil. The solvent is used without addition of water andits content of water should be 2% by weight or less. The use ofsubstantially anhydrous methanol, ethanol or acetone is most preferable.The raw material should not be previously immersed in water nor crushed.The grinding machine is of the wet milling type. This grinding is notmere crushing, and a hammer mill or a jet crusher is not suitable fortheir use. Proper devices are a dispersion mill, an agitation mixer, ora homogenizer. These devices perform a grinding or triturating actionsimultaneously with an emulsifying action. Any grinding machine of thewet milling type which can grind the fibrous portion of the raw materialto a moderate size of minimum 30 to 40 mesh can be used. This grindingeffects a penetrating action and a cell-wall rupturing action on the rawmaterial. The mixture acquires the proper viscosity for this action bymixing the moisture of the raw material with the dissolved components.The fibrous portion is left in moderate (relatively coarse, minimum 30to 40 mesh in size) size easy to separate. This grinding action periodshould be from 5 to 20 minutes and a longer or shorter grindingoperation is not necessary. The completion of the grinding operation canreadily be determined by observation of the solids, which will be in theabovenoted state.

In contrast to this wet grinding action, when the fiber is treated foronly a short time with heavy grinding as by a hammer mill, it is groundinto a minute size, and extraction by the first solvent is not carriedout completely, making it difficult to accomplish the object ofseparation of undenatured protein of good quality.

.After completing the said novel treatment, the solid matter isseparated from the solution by a conventional process (e.g. filter,centrifuge, etc.). With the separated extract solution there aresimultaneously removed coloring substances that would be likely to beabsorbed subsequently on the protein, and bitter principles, in additionto substances normally removed when purifying oil, thus improving thequality of the protein.

The thus obtained solid matter can be freed from the solvent attemperatures lower than that of denaturation of the protein because itis powdery, and the water content is about 5%.

Afterwards, the solid matter is treated with an ordinary fat removingsolvent such as 3 to 5 times (by weight) of hexane, isopropyl alcohol,benzene, toluene, etc., and there are obtained after removing thesolvent oil of good quality and solid powder. When this dried powder isclassified with a 60- to IOO-mesh sieve, it is easily separated into afibrous portion and a sweet tasting and nutritious white fine powdercontaining protein. This fine powder is characteristically smaller than150 mesh in size and the fibrous part is mostly larger than 40 mesh, andthe fibrous portion and hull are thus ordinarily completely separatedwith 60- to mesh sieves.

The present process not only separates oil, nutritious component, andfibrous portion, but also the oil and nutritious components are betterin quality than the conventional product, and it is furthercharacterized in that it is carried out easily in industrial productionand in a short time.

EXAMPLE 1 Samples comprising one hundred grams of soybeans (watercontent 11.06%, oil 15.25%) were mixed with 300 grams of methanolcontaining 0, 10, 20, 30, and 40% of water, respectively, ground with amixer for 10 minutes, and then filtered with ordinary filter paper(suction filtration) to obtain filtrate A; the residue was dried at 70C. for 1 hour to obtain intermediate product (B); the dried residue wasfreed from fat with 300 grams of n-hexane, and neutral oil (S) wasproduced after distillation of hexane; and the separated solid matter(D) was classified with a 60-mesh sieve into fibrous part (E) and powder(F) after drying.

In the above examples the first solvent can be methanol, ethanol,acetone, or mixtures thereof containing up to 2% water.

Time of (A) Residual Quantity offiltration water con- Portion ofQuantity Residual to obtain tent of soybeans of neutral oil in FibrousAmount of water in filtrate A, intermediin methoil soild (D) fractionPowder methanol (percent) sec ate product anol (g.) (g.) (percent) (E)(8-) (F) (g.)

EXAMPLE 2 The embodiments of the invention in which an exclusiveproperty or privilege is claimed are defined as follows:

In procedure A of this example, one hundred grams of rice bran (watercontent 12%, oil content was mixed with 200 grams of anhydrous methonoland ground with a mixer for 12 minutes and filtered; then the solidmatter was dried at 70 C. for 1 hour, freed from oil with hexane andthereafter classified with an 80-mesh sieve. For comparison, inprocedure B one hundred grams of said rice, which had been dried to awater content of 5% and an oil content of 21%, was ground in 400 gramsof hexane for 12 minutes and, after filtration, the solid matter wasclassified subsequently to the drying.

As will be clear from the above examples, the present process isadvantageous from the viewpoint of the production process. As for theseparated product, it has been demonstrated that, when oil is extractedwith an oil solvent from the raw material containing more than 10% ofwater content, a dark-brown substance exists in the extracted oil and itis difiicult to decolor the oil by purification. According to thepresent invention, since the water content is less than 6% when oil isextracted, no such difliculty arises. The advantage of this process liesin that colored substances, free fatty acids, odorous substances, andwax usually removed in the purification process are mostly removed inthe previous treatment with the organic solvent. Further, the cell-wallis broken into powder so that fats and oils may be completely extractedwith a fractional part 6% to A of the quantity of solvent usuallyrequired for oil removal. Furthermore, the extracted oil is mostly ofsuch high quality that a further purification is not necessary. When theextracted oil is to be used as salad oil, the extracted oil can beprepared as a final product by a much more simple refining method. Thesolid matter which is freed from the oil is powdery so that it can befreed of solvent at temperatures far lower than in the conventionalmethod, thus hardly causing any thermal denaturation of the containedprotein. The thus obtained dried powder is separated into fibrous partand nutritious part containing protein.

1. A process for separately recovering neutral oil and a protein-richpowder from oil-bearing material selected from the group consisting ofraw seeds, corn germ and rice bran, said oil-bearing material containingundenatured protein, more than 6 weight percent water, fibrous material,and impurities comprising carbohydrates, color material, wax material,free fatty acids, and odor and taste principles, which comprises mixingone part by weight of said oil-bearing material with a first solventconsisting of about 1.5 to 4 parts by weight of a water-miscible solventselected from the group consisting of methanol, ethanol and acetone andmixtures thereof, said first solvent containing no more than 2% byweight of water, and grinding the mixture under wet milling conditionsto extract water and said impurities into said solvent to form a firstliquid extract phase and the remainder of the mixture forming a firstsolid phase containing undenatured protein, neutral oil, fibrousmaterial and less than 6 weight percent water; separating said firstliquid extract phase from said first solid phase; mixing said firstsolid Phase with an oil extracting organic solvent until the neutral oilin said first solid phase dissolves in said oil-extracting solvent toobtain a second liquid phase enriched with neutral oil and a secondsolid phase; separating the second liquid phase from the second solidphase and recovering neutral oil from said second liquid phase; dryingthe second solid phase to obtain a finely divided powder; and passingthe powder through a sieve of a size in the range of 60-100 mesh toseparate the powder into a protein-rich fraction which passes throughthe sieve and a fraction composed primarily of fibrous material whichremains on the sieve.

2. The method of claim 1 in which the oil bearing material is soybeans.

3. The method of claim 1 in which the oil bearing material is rice bran.

References Cited UNITED STATES PATENTS 2,879,167 3/1959 Grandel 99-80 G3,295,985 1/ 1967 Cavanagh 99-17 3,542,559 1/ 1970 Goodban et al 99-17 X3,615,655 10/1971 Freeman et al. 99-17 A. LOUIS MONACELL, PrimaryExaminer J. R. HOFFMAN, Assistant Examiner US. Cl. X.R.

